Picture of Altoids USB Battery/Solar charger for iPhone and iPod
I know there are plenty of USB chargers out there for you to build.  But here's one that doesn't use a voltage regulator or an IC chip to power it.  The basic concept is to use 4 - AAA rechargeable batteries (1.2V a piece) to power the USB and a couple of solar cells to charge the batteries.  If you've done the basic math you're probably wondering how 4.8V (4 x 1.2) is going to power a USB device which requires 5VDC.  Well that's actually how I came up with the idea.  I have another charger I made using a 9V battery and a 5V regulator.  It will charge my iPod until the battery runs low.  When I test the voltage output at the USB with a spent 9V, it will be spitting out 4.7V.  So that's the cut off point.  4.8V is still within the tolerance for a USB device to charge.  So I tried a 4-cell setup on my breadboard and it worked!  I tested the voltage at the USB socket and (to my surprise) it was at 5.2V.  I put my voltmeter on each battery and they were cranking out 1.3V at full charge.  This is great!  The tolerance of a USB happens to be just right for these four cells.  So the solar part was sort of an afterthought for charging the batteries (they are rechargeable anyway).

If you'd like to try to make one yourself, here's what you need:

4 - AAA Battery Holder

USB Socket (female)

Solar Panel (3V output minimum, around 5V max)

Blocking Diode (not LED)

Some resistors (This is somewhat optional.  You need them if you want your iPod/iPhone to recognize your charger.  I'll explain exactly which ones to use later.)

DPDT Toggle Switch

Small Perf Board (Also optional)

Soldering Iron

Step 1: Prepare the tin

Picture of Prepare the tin
I started with an easy step.  Paint the tin.  I just wanted to start with a blank canvas.  You do too... trust me.
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bear825626 days ago

Why is there never a good video for ppl like me who more visual? I don't understand the way it was explained

txcoasty2 months ago
Could you please send me the walk through for the switch and light txcoasty@gmail.com
ssingh1637 months ago
I use 7805 votage regulater 2 100 ohm resistor to d+ or d- 8 aa rechargable cell 4 cell hav 1000 mah so 8 cell have 2000 mah but prblm is tht my iphone shw charging but not increase the battery persentage it decreased after few sec n min plz help me i use 2 cell holder 1 holder capacity is 4 cell i use cell series or parralel but not working
Sheppi8 months ago


great insructable but my iphone just shows the charging icon but doesnt actually charge

pooyathr2 years ago
It means that if we wana to charge an android device we don't need resestors?
Plz answer as soon as you can.
haikuordie (author)  pooyathr2 years ago
Yes. It means you don't need the resisters. Apple devices require voltage to the data pins but most others do not.

I just read that:

The IEEE USB charger standard requires dumb chargers (those like yours without the extra electronics required to signal that they are a charger) have their data pins shorted to each other, so the phone will recognize that this is just a charger, not a USB port and start charging immediately otherwise it waits for the USB bus allocated address.

This was a post on a forum and I have not verified it by trying to find the IEEE specifications.

I want to make a battery pack charger that only uses batteries, their holder and a USB connection--I never travel without lots of rechargeable batteries and can recharge them during the stops with my standard charger for the camera.

Comments anyone

just did this on a bread board. It worked! Thanks for posting this.
neemanee1 year ago
As quickly as possible would be nice. thanks again
neemanee1 year ago
neemanee1 year ago
Can you make a video? Please
haikuordie (author)  neemanee1 year ago
I'll see what I can do. I have to make another of these anyway.
why do you need a blocking diode?
JKPieGuy1 year ago
Wouldn't a voltage regulator work aswell?
Okay where in the circuit would I put it?
haikuordie (author) 1 year ago
A 100k ohm pot. would work and be easy to find. The smaller the pot. the easier it would be to set it just right. If you don't know how to use a pot. for a voltage divider it would take me a lot more space to explain it then in this comment section. It's not difficult to do, it's just hard for me to explain without pics.
And what kind would I get?
If I was going to go the potentiometer route were would I put it at in the circuit?
haikuordie (author) 1 year ago
Regular 1.5volt batteries won't work. That gives you too much voltage. I used rechargeable for that very reason. NiMH rechargeable batteries are 1.2volts a piece. This is all on the i'ble. If you can't use rechargeable, you should use a potentiometer for a regulator. That would work.
As far as I know I'm just using regular 1.5 alkaline AA batteries from SAMs (I wasn't going to get rechargeable till I got it to work) how do I get it down? Maybe another resistor?
haikuordie (author) 1 year ago
Levi: it looks like they are wired correctly and you are using the right resistors. That's a step in the right direction. Your voltages are all way off. You need to do something about the input voltage. How are you getting 6.37 VDC from four 1.3 volt batteries? Are you using NiCd instead of NiMH? The voltage from positive to ground needs to be very close to 5VDC. then your other voltages should come out fine when that happens.

If you have anymore questions you can write me at myk@haikuordie.com. I can respond easier that way.
Okay I have put it all on a perf board and I used a multi meter I have the settings on 20DCV and I'm reading ground to positive 6.37 ground to data + 3.18 ground to data - 2.53…sorry all I had was red and white cables
13, 6:53 PM.jpg13, 6:53 PM.jpg13, 6:53 PM.jpg
haikuordie (author) 1 year ago
Levi: It looks from the pics that you may have the pins backwards. It's hard to tell. The best way to diagnose the issue would be with a digital multimeter. Make sure you are getting the correct voltage to the correct pins.

One way to see if the wires are at least somewhat correct is to see if this will charge an android phone or other device. I don't suggest doing this with something you really care about unless you are sure it is pinned right. If it will charge something other than an iDevice, you can try switching the wires to the middle pins. If this doesn't work, you really need to find out what the voltages you're getting to the various pins. You may have a resistor working outside its tolerance or maybe your batteries are giving a strange voltage (more or less than required).
Hey sorry I don't have any perf board and I'm kinda new can you tell me what I'm doing wrong? For some reason my iPhone wont recognize it. I just took off the switch till I get it recognizing

Please any info would help
13, 11:25 PM.jpg13, 11:25 PM.jpg
When it says "blocking diode" will any diode work(other than LED)?
I Googled Blocking Diode, and they are a few dollars, But i have my own diodes, will they work as long as they are rated above the maximum output of the Panels?
haikuordie (author)  austin2118ace1 year ago
Yes. Any diode should work.
hi austin i'm pretty sure that all diodes will work as they serve the same function.
Schmidty162 years ago
Why not 3 solars
haikuordie (author)  Schmidty161 year ago
I didn't have the room on the project box.
mmarcuzzo2 years ago
Would it work if i had 2 round solar panels that are about an inch in diameter? Or would they be to small
haikuordie (author)  mmarcuzzo2 years ago
That sounds a bit too small but it really depends on their output. I think the range can be found somewhere in this i'ble.
timrim2 years ago
Hey could u send pic of the front of the board thanks
haikuordie (author)  timrim2 years ago
I would if I still had this charger, but I do not. Please refer to step 5 where I gave a color-coded diagram of what this board should look like.
iliceras2 years ago
Thanks for this amazing project. Let me ask you some questions:
- I've seen similar projects with no switch, is that possible? I mean, can we chager the battery pack at the same time a device is being charged by the usb connection?
- 4AA or 4AAA battery pack would get 4.8v at fully charged, but it's getting lower they are draining, will it still work? why don't you place a DC-to/USB converter to get always 5v from 3v-4.8v output battery pack voltage?

Thanks in advance
haikuordie (author)  iliceras2 years ago
Thanks for your comment. First, you CAN do this without the switch (I'd guess you're referring to the series-to-parallel switch). I only used this to save the project from needing solar cells that are larger than the tin. You CAN charge the battery pack and a USB device at the same time. You would need a solar cell capable of doing this. My guess is you'd want to obtain a large one that puts out more voltage and amperage than is needed and add a regulator. This, of course, would complicate things by making it larger and less convenient... but to each his own. =)

I'm not sure I understand what you're asking about the battery pack. I chose to use 4 rechargeable batteries in order to make this as simple as possible... meaning without the need for a regulator or a charge-pump. There are a couple of projects out there that use these and I'm sure work well. If you want to modify my project and integrate a system from another project, I would love to see the results.

Hey there great post just needed some help i'm basing a similar project and trying to fit it into an altoids smalls hopefully I can get it all together to share on here. But I have a question I made a similar setup and wanted you to check it I ran the circuit on a simulator and this was my result the numbers are a bit different than yours can you tell me if it would still be safe for my devices and would it work?
Altoid Smalls Solar panel - USB Charger.png
haikuordie (author)  danielparedes2 years ago
It looks like a pretty good schem. The only trouble I can see with it is the solar cell. If this is in full sun it will be producing 6vdc which is more than you want to power the usb with. It also might not be enough tto charge the batteries if your cell is the least bit shaded. If you plan on only plugging in devices when it's in the shade this should work out okay for you.
kaylee_ct2 years ago
I have no idea what kind of "board" you're talking about. It is not mentioned in the materials list. I am just so confused right now. If anyone can help, it would be greatly appreciated.
haikuordie (author)  kaylee_ct2 years ago
The materials list has a "Small perf board". It's the type you can buy at places like Radio Shack. They typically call it a "project board" but it is often call a perferrated board. I said that it was optional because you can always solder the parts together without any board if you're a well-seasoned solderer. I don't suggest this BTW. I only put it out there because I've done this a great many times myself when I was in a pinch and just wanted to try out a circuit (I use a breadboard for such endeavers nowadays). I hope this isn't your first project. I know I've messed up many a component trying to do a project I wasn't ready for. Message me if you have any other questions.

pmvinuelas2 years ago
if you wanted to remove the batteries and have the solar panels directly charge your iphone, how big would you need the panels to be?

I am looking to have something that can charge my phone while i am outside but want it as small and light as possible. I figured if i removed the batteries i would just need to make sure i had enough power from the solar panels to come in and some sort of charge regulator right?

Thanks for the help.
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